Zika Virus: the Latest Newcomer

Abstract

Since the beginning of this century, humanity has been facing a new emerging, or re-emerging, virus threat almost every year: West Nile, Influenza A, avian flu, dengue, Chikungunya, SARS, MERS, Ebola, and now Zika, the latest newcomer. Zika virus (ZIKV), a flavivirus transmitted by Aedes mosquitoes, was identified in 1947 in a sentinel monkey in Uganda, and later on in humans in Nigeria. The virus was mainly confined to the African continent until it was detected in south-east Asia the 1980's, then in the Micronesia in 2007 and, more recently in the Americas in 2014, where it has displayed an explosive spread, as advised by the World Health Organization, which resulted in the infection of hundreds of thousands of people. ZIKV infection was characterized by causing a mild disease presented with fever, headache, rash, arthralgia, and conjunctivitis, with exceptional reports of an association with Guillain-Barre syndrome (GBS) and microcephaly. However, since the end of 2015, an increase in the number of GBS associated cases and an astonishing number of microcephaly in fetus and new-borns in Brazil have been related to ZIKV infection, raising serious worldwide public health concerns. Clarifying such worrisome relationships is, thus, a current unavoidable goal. Here, we extensively review what is currently known about ZIKV, from molecular biology, transmission routes, ecology, and epidemiology, to clinical manifestations, pathogenesis, diagnosis, prophylaxis, and public health.

Keywords: Zika; flavivirus; microcephaly; outbreak; zoonosis.

FIGURE 1

Schematic view of Zika virus (ZIKV) genome organization. The open reading frame (ORF) (boxes) that encodes structural and non-structural proteins is flanked by two untranslated regions (UTR). The proportion of each region was calculated from the ZIKV MR766 sequence available at GenBank (NC_012532.1). Scale bar: 1 kb.

FIGURE 2

Schematic view of the ZIKV cellular lifecycle. See text for details.

FIGURE 3

Representative phylogram showing the relationships between strains of the genus Flavivirus. Accession numbers are displayed in the tree. The arrow indicates ZIKV. The scale indicates 0.2 substitutions/site. The tree was based on complete NS5 nucleotide sequence, built from a multiple alignment using Clustal omega and Phylogeny.fr (Dereeper et al., 2008).

FIGURE 4

Representative phylogram showing the relationships between ZIKV strains. The accession number, country of isolation and year is displayed in the tree. The scale indicates 0.03 substitutions/site. The tree was based on complete NS5 nucleotide sequence, built from a multiple alignment using Clustal omega and Phylogeny.fr.

FIGURE 5

Map showing worldwide autochthonous and imported ZIKV human cases since the last 9 months. See text for details.